Hi,
If you're not into networking, the method I use will probably seem like too much work but I'll offer it up just the same.
I'm still using an S4 with 4.4.4 on it btw...
There's a utility that's been around for ages called netcat. It's a linux utility that was developed on Linux but has been ported to Windows as well.
Netcat runs on the command line and it's very lightweight. You can use it to listen on a port (TCP or UDP) or send to a listening port.
It would take too long for me to write a whole tutorial but you can google it and find out more about it.
You can download Netcat for Windows and to run it on your phone, you'll need to download a terminal emulator from the play store and then install either BusyBox (which I think you need root for), or Kbox, which is what I have. Kbox comes with a whole suite of stripped-down Linux built-ins, one of which is Netcat.
You run it on your terminal like: nc {options}
I've been using it for 20 years and can't imagine life without it but then again - I'm weird like that.
